A spoof ad campaign offering surfers the chance to infect their PCs with malware has drawn plenty of interest.

In an experiment, a security researcher bought a Google ad campaign to promote a site ostensibly offering to infest visitors' Windows PCs with computer viruses. The "click here to be infected" campaign was displayed 259,723 times and clicked on 409 times, at a click-through rate of 0.16 per cent or around one in 500. The cost of the six-month campaign was $23, or around 5c per chance to infect a PC.

That's the kind of figure that might be recouped by selling access to compromised zombie machines, providing hackers had enough funds up front, although there are undoubtedly cheaper ways to achieve the same objective. "I'm sure I could get much more traffic with a higher Google Adwords budget and a better designed ad," Didier Stevens writes.

The ad was pretty unambiguous in its intent:

Drive-By Download Is your PC virus-free? Get it infected here!

Users clicking on the ad were directed to the domain drive-by-download.info domain. Domain featuring .info are notorious for hosting malware. In this case, no malware or scripts were ever hosted on the site, but those visiting the site weren't to know it was just an experiment.

It'd be nice to think that those that clicked on the ads were cyber-savvy types with fully patched systems who were simply curious about the bizarre offer. But we doubt it.

As the SANS' Institute's Internet Storm Centre notes, the experiment provides evidence that some people will "click on anything".

Tricking users into visiting sites contaminated with malicious scripts has begun to outpace malware-infected email as the main means to deliver malware over recent months. Didier Stevens' experiment provides evidence that such malware trickery might be effective even without convoluted redirection chains or elaborate deception schemes, further illustrating how dangerous it is to visit "dodgy" websites.